An operating system provides an extensible share action to broker content sharing between applications executing on a computing platform such as a personal computer, tablet computer, or smartphone. The share action enables a consistent user experience for content sharing to be implemented across all applications and eliminates users having to switch from the current application they are using to some other functionality in order to share content. Applications can participate with the operating system share action as source applications and/or target applications. Source applications may describe what content is shareable given the current state of their application when the user chooses to invoke the share action. Target applications can be configured to receive the shared content from the source application according to content type, and will expose a companion view of their application to the user that is specifically tailored to facilitate sharing.